Immediately prior to ovulation, pituitary secretion of LH increases dramatically resulting in a surge of circulating LH which signals ovulation. While this is obviously a critical event for normal reproductive function, the mechanisms subserving this LH surge are poorly understood. Quantitative changes in LH secretion as well as qualitative changes in secreted LH are believed to underlie this surge. A coordinated series of clinical and laboratory experiments is proposed to investigate some of these mechanisms. Serial blood samples collected during the LH surge in women and in the rat will be obtained and assayed for LH. The resulting hormone concentration time series will be analyzed using simultaneous multiple parameter deconvolution to assess quantitative changes in LH secretion i.e. alterations in amplitude and/or frequency of secretory episodes. In the laboratory, a series of in vitro experiments is planned to examine the processing and secretion of LH before and during the LH surge as a correlate to, and possible explanation for, changes in pituitary responsiveness to GnRH and/or changes in bioactivity of the hormone. These investigations will focus on qualitative changes in secreted LH and will include assessment of whether the relative content of isoforms of LH (which presumably reflect states of glycosylation and provide for certain bioactivity attributes) changes, and if so, where during intracellular transport these changes occur. Fast protein liquid chromatography will be used to resolve isoforms of LH secreted before and during the surge as well as LH in various intracellular compartments. Using pulsechase techniques, information about pathways of LH release during the surge will be obtained. Results of this series of experiments will provide valuable insight into this crucial event in reproduction.